AR 15 SP1

Hi, I have in mind to purchase a Colt AR15 and have been offered a sp1 in what appears to be great condition with an attached scope and 500 rounds of military surplus ammo for $1500. The seller is the original owner and has not fired the weapon for about 15 years. Is this a fair price? I didn't write down the name of the scope but I know it is an old one and has been with the rifle since its initial purchase. There is also a box with 10 extra magazines. Any opinions out there?